Many industries have a need to process thin and flexible workpieces. For example, flat panel display industry requires processing of large pieces of thin glass sheets, e.g., having lateral dimensions (length and width) of tens of centimeters to meters, and thicknesses of less than one millimeter. In many cases, any unnecessary physical contact of the workpiece with a surface or object, e.g., contact that is not required for processing of the workpiece, may risk scratching or otherwise damaging or marring the workpiece.
A common solution is to support the workpieces on a noncontact support platform. A noncontact support platform typically includes a tabletop that is configured to form an air cushion above the tabletop. For example, the tabletop may include a distribution of pressure ports out of which air is forced above the tabletop. In many cases, vacuum ports to which suction is applied are interspersed among the pressure ports.
When a workpiece is rigid, local bending of the workpiece may be negligible. In this case, if the air cushion that is formed by the noncontact support platform is sufficiently thick, the workpiece may be supported at a uniform distance from the tabletop and there may be no risk of contact between the workpiece and the tabletop.
However, if the workpiece is flexible, and if the force exerted by the air cushion that is formed is not uniform below the workpiece, the workpiece that is supported by the air cushion may bend or dimple. For example, in some cases, the dimpling may form an “egg crate” pattern on the workpiece. In this case, part of the workpiece may bend or sag toward the tabletop, risking contact between the workpiece and the tabletop. In addition, non-uniform support of the workpiece may adversely affect a manufacturing or inspection process that is being performed on the workpiece.